A typical thin and fully flexible hybrid electrode was developed by integrating the encapsulation of silver nanowires (AgNWs) network between a monolayer graphene and polymer film as a sandwich structure. Compared with the reported flexible electrodes based on PET or PEN substrate, this unique electrode exhibits the superior optoelectronic characteristics (sheet resistance of 8.06 Ω/□ at 88.3% light transmittance). Meanwhile, the specific up-to-bottom fabrication process could achieve the superflat surface (RMS = 2.58 nm), superthin thickness (∼8 μm thickness), high mechanical robustness, and lightweight. In addition, the strong corrosion resistance and stability for the hybrid electrode were proved. With these advantages, we employ this electrode to fabricate the simple flexible organic light-emitting device (OLED) and perovskite solar cell device (PSC), which exhibit the considerable performance (best PCE of OLED = 2.11 cd/A; best PCE of PSC = 10.419%). All the characteristics of the unique hybrid electrode demonstrate its potential as a high-performance transparent electrode candidate for flexible optoelectronics.
The development of thin film dielectrics having both high energy density and energy conversion efficiency, as well as good thermal stability, is necessary for practical application in high‐temperature power electronics. In addition, there is a demand for the development of new Pb‐free high‐energy density dielectric materials due to environmental concerns. In this regard, thin films of weakly coupled relaxors based on solid solutions of BaTiO3–BiMeO3 have shown good promise, because they exhibit a remarkably large polarization over a wide temperature range. Nevertheless, the performance of Pb‐free thin films has lagged behind that of their Pb‐based counterparts in terms of thermal stability and energy conversion efficiency. Toward this end, most recent studies on BaTiO3–BiMeO3 systems have focused on the optimization of material composition, while relatively less attention has been paid to other aspects such as defect chemistry and crystallographic texture. In this study, we examine the effects of A‐site vacancy and crystallographic texture on the energy storage performance of BaTiO3–BiScO3 thin films synthesized using pulsed laser deposition (PLD). It is shown that a high energy storage density (Wr) of ~28.8 J/cm3 and a high efficiency of η >90% are achieved through a combination of moderate A‐site vacancy concentration and (110) crystallographic texture. Furthermore, Wr remains nearly temperature independent while a high efficiency of η >80% is maintained for temperatures up to 200°C, which constitutes one of the best performances for Pb‐free ferroelectric films for high‐temperature capacitor applications.
ABO3 perovskite ferroelectric thin films have gained wide attention in recent years for high density capacitive energy storage applications. In this regard, BaTiO3–BiMeO3, where Me is a metal cation, are particularly promising materials because of their high electrical polarization and low hysteresis losses. However, for a broader adoption of BaTiO3–BiMeO3 thin films in advanced electronics applications, it is necessary to maintain good thermal stability in addition to high energy density and energy storage efficiency. In this work, we show that a superior combination of these characteristics can be obtained through the control of different defect concentrations, viz., A-site cation vacancies (VA) and B-site ionic substitutions (MeTi). It is shown for BaTiO3–BiScO3 thin films that an optimum combination of VA and ScTi leads to a high energy storage density of 40.5 J cm–3 and an efficiency higher than 85%, which could be maintained from room temperature to 200 °C. A mechanistic understanding of the enhanced energy storage performance based on the synergistic effect of random fields introduced by A-site vacancies and strong hole trapping by ScTi acceptor centers is proposed. Perovskite ferroelectric thin films capable of maintaining high performance at high temperatures may facilitate the advancement of power electronics applications in harsh environments.
Oxygen octahedra tilt (OOT) transition is the most common type of distortion in inorganic ABO3 compounds with a perovskite crystal structure. The importance of OOT transitions is underlined by accompanying changes in the B-O and A-O bonding environments, which consequently affects the electronic states and hence influences electrical, magnetic, and superconducting properties of many perovskite compounds. In recent years, controlled manipulation of the OOT order in perovskite thin film ferroelectrics has been attempted through heteroepitaxial strain engineering. The current study demonstrates an alternative approach whereby OOT ordering in a 200 nm thick polycrystalline thin film of (Na1/2Bi1/2)TiO3 (NBT) Pb-free ferroelectric is induced by applying electric-field along the 111 octahedral tilt axis, which is furthermore enabled by a strong (111) crystallographic texture normal to the film surface. In situ x-ray diffraction reveals that electric-field-induced OOT ordering proceeds through nucleation and rapid growth of domains with ordered a−a−a− tilting, followed by an increase in the tilt angle within the ordered domains.
Although lead (Pb)-based ferroelectric thin films are widely used in many electronic devices, alternative Pb-free materials have been widely investigated in recent years to address concerns about Pb toxicity. In this regard, past research has primarily focused on the design of solid solutions of different Pb-free perovskite oxides to obtain optimum properties. However, the effect of a film–electrode interface on the functional properties of thin films of the recently developed Pb-free ferroelectrics has been largely ignored. This is surprising since the quality of the film–electrode’s interface is known to inherently affect the crystallinity and growth direction of the overlying film microstructure. Here, we have addressed this important issue for the ferroelectric thin film of BaTiO3–BiScO3 (BSBT), which is attractive for high-temperature capacitor applications. Using high-resolution transmission electron microscopy (TEM) imaging and energy-dispersive X-ray spectroscopy, we show that controlled diffusion of cations and oxygen ions across the film–electrode interface and elimination of a detrimental amorphous layer promotes semiepitaxial growth of the 110-textured BaTiO3–BiScO3 (BSBT) films on a Pt-electrode. The changes at the film–electrode interface prove to be crucial in enhancing the energy density of the BSBT/Pt film heterostructure to a maximum of ∼30 J cm–3 and the overall energy efficiency to an impressive 90%. The current results highlight the significance of interfacial diffusion on the functional properties of Pb-free ferroelectric thin films.
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